Safety arrangement in a motor vehicle

ABSTRACT

A safety arrangement in a motor vehicle comprises a seat to be occupied by a passenger of the vehicle. The seat is supported by a framework ( 32, 33 ). The framework is mounted on to a carriage ( 6 ) by four deformable members ( 5 ) each having sensor means responsive to deformation of the deformable members. The sensor can determine the weight of a person sitting on the seat and also the position of that person within the seat. The sensors are associated with controls adapted to initiate and control the inflation of an air-bag when an accident arises. The inflation characteristic of the air-bag can therefore be adapted to the weight and position of the occupant of the seat.

BACKGROUND OF THE INVENTION

THE PRESENT INVENTION relates to a safety arrangement in a motorvehicle.

It has been proposed to provide safety arrangements in a motor vehiclewhich incorporate an air-bag adapted to be inflated in the event that anaccident should occur to provide protection for the driver or anoccupant of a vehicle. It has been customary to mount an air-bagintended to provide protection for a front seat passenger of a motorvehicle in the event that a frontal impact should occur within thedashboard of the motor vehicle. The air-bag is associated with anappropriate sensor arrangement which initiates inflation of the air-bagin the event that a frontal impact should occur.

When the air-bag is inflated, the fabric of the air-bag may be given, atleast initially, a very substantial velocity directed towards theoccupant of the front seat. If the occupant of the front seat is not inan appropriate position, that is to say, is not sitting fully back inthe seat, then difficulties may arise. If, for example, the occupant ofthe seat is leaning forwardly at the instant that the air-bag isinflated, the air-bag may impact severely with the occupant of the seatand may impart substantial injuries to the occupant of the seat.

If the occupant of the front seat is very heavy, then the occupant ofthe seat will require much more “cushioning” in the event that a frontalimpact should arise than a very light occupant of the seat. Thus, it isdesirable to be able to inflate an air-bag which has been provided toprotect the occupant of a front seat in the event of a frontal impact,in dependence upon the weight of the occupant of the seat.

It has been proposed before to control the inflation of an air-bagprovided to protect a front seat passenger in a motor vehicle. DE OS2516185 discloses an arrangement in which a switch is provided withinthe squab of the seat. If the occupant is sitting on the seat, theswitch is closed, and in the event that an accident should occur, theair-bag is fully inflated. However, if the switch is not closed, whichis a situation which might obtain if the occupant of the seat is notactually sitting on the seat, but instead is standing in front of theseat, then the air-bag is only partially inflated.

DE 3809074 also discloses an arrangement in which sensors are locatedbetween the squab of the seat and the floor of the motor vehicle todetermine the downward forces applied at the front and at the rear ofthe seat, to determine the position of the occupant of the seat and thusto control the inflation characteristic of an air-bag.

Sensors that have been utilised previously have been designed to resistthe forces which may be applied to the sensors in an accident situation.These forces can be extremely high. It has proved to be extremelydifficult to provide a sensor which has sufficient strength, but whichcan provide a reliable and accurate determination of the forces appliedto the seat during ordinary driving conditions. Many of the sensors thathave been used before are such that the measurement of the force isdetermined as a consequence of a movement of one part of the sensorrelative to another part of the sensor. Any frictional effects betweenthe two parts of the sensor causes the sensor to provide an incorrectreading and also, if the occupant of a seat changes position there maybe a substantial time delay (at least relative to the time available toinflate an air-bag during an accident situation, which is usuallymeasured as a few tens of milliseconds) before a correct output signalis provided.

BRIEF SUMMARY OF THE INVENTION

The present invention seeks to provide an improved safety arrangement.

According to this invention there is provided a safety arrangement in amotor vehicle, the safety arrangement comprising a seat to be occupiedby a passenger of the vehicle, a plurality of sensors located betweenthe seat and the floor of the vehicle, each adapted to provide anindication of the downward force applied to it, control means adapted toinitiate and control the inflation of an air-bag and adapted to receivesignals from the sensors, and adapted to control the inflation of theair-bag in dependence upon the nature of the said signals, the sensorscomprising means which, at least in ordinary use of the seat, form thesole connection between the seat and the floor of the motor vehicle,each sensor comprising a first portion connected directly or indirectlyto the floor of the motor vehicle, and a second portion connecteddirectly or indirectly to the seat, said two portions beinginter-connected by a deformable element having sensor means responsiveto deformation thereof.

Preferably the first portion of each sensor is mounted on a carriageslideable along a rail mounted on the floor of a motor vehicle and thesecond portion of each sensor is connected to a sub-frame of the seat.

Conveniently the element inter-connecting the first and second portionsof each sensor comprises a cantilever beam adapted to deflect when adownward force is applied to the portion connected to the seat.

In one embodiment the cantilever element has one end connected to amounting block comprising said first portion, the mounting block havingmeans securing the mounting block to part of the carriage, and has theother end connected to a mounting block, that other mounting blockhaving means securing the mounting block to part of a sub-frame for theseat.

In an alternative embodiment each sensor comprises an integral element,the element having a first portion mounted to a carriage slidablymountable in a rail connected to the floor of the vehicle and a secondportion connected to the sub-frame of a seat, the two portions beinginter-connected by a cantilever element.

Preferably part of the carriage is located adjacent part of thesub-frame, one of said parts carrying a projection of a predetermineddiameter, said projection being located within an aperture of slightlygreater diameter formed in the other part, the arrangement being suchthat in the event that a substantial force is applied to the seat, theprojection carried by the one part will engage the wall of the aperturecarried by the other part.

Conveniently the said one part comprises a web carried by the carriage,and the other part comprises a flange carried by a support elementforming part of the sub-frame, the carriage carrying a bolt having athreaded portion passing through a bore provided in the web and having aportion of enlarged diameter, defining a shoulder with the threadedportion, the portion of enlarged diameter extending through saidaperture which is formed in a flange provided on a support elementforming pail of the sub-frame of the seat.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, and so thatfurther features thereof may be appreciated, the invention will now bedescribed, by way of example, with reference to the accompanyingdrawings in which:

FIG. 1 is a schematic illustration, which comprises a partial blockdiagram, illustrating a vehicle seat for a front seat passenger in amotor vehicle, and an associated air-bag, together with a controlarrangement,

FIG. 2 is a perspective view of the sub-frame for the seat as shown inFIG. 1, and associated carriages on which the sub-frame is mounted formovement along rails (which are shown in phantom),

FIG. 3 is an enlarged view of a load cell forming a mounting element asshown in FIG. 2,

FIG. 4 is an enlarged view of an alternative form of load cell, and

FIG. 5 is an enlarged sectional view illustrating a bolt arrangementsecuring the sub-frame of FIG. 2 to the carriage of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Referring initially to FIG. 1 of the accompanying drawings, a vehicleseat 1 is illustrated having a squab 2 and a back 3. The squab 2 isconnected by means of four sensors, (only two of which 4, 5, are visiblein FIG. 1) to two carriages, (only one of which, 6, is visible in FIG.1), which are mounted on a pair of rails (only one of which, 7, isvisible in FIG. 1) which are mounted on the floor of a motor vehicle.The seat is provided with two sensors 4, 5, along each side of the seat,one sensor 4 being located at the front of the seat, and one sensor 5,being located at the rear of the seat.

The sensors 4, 5 are connected to a control arrangement 8 which alsoreceives signals from further sensors 9 which are responsive to anaccident or a situation when an accident is likely to occur. Thus, thesensors 9 may comprise acceleration sensors or impact sensors.

The control device 8 is connected to an air-bag arrangement 10 mountedin the dashboard 11 in front of the seat 1. The control arrangement 8can initiate inflation of the air-bag 10. The control arrangement 8 canalso control the manner in which the air-bag is inflated. For example,the air-bag may be provided with two pyrotechnic gas generating charges.The control arrangement may activate either one of the charges, or theother of the charges, or both of the charges, thus providing threedegrees of inflation of the air-bag. Alternatively the controlarrangement may, in certain circumstances, activate neither of thecharges and the air-bag will remain uninflated. The control arrangement8 can, of course, also control the instant at which inflation of theair-bag is commenced.

Referring to FIG. 2, the squab 2 of the seat 1 is mounted on a sub-frame20 which is illustrated in FIG. 2. The sub-frame 20 is mounted on thecarriages 6 which are mounted for axial sliding movement on the rails 7.The sub-frame, the carriages and the rails are substantially symmetricalabout the mid-point of the sub-frame.

In FIG. 2, the rails 7 are shown in phantom. Each rail is provided, atits forward end, with a clip 21 by means of which the forward end of therail is secured to the floor of the motor vehicle. The rear part of eachrail, as illustrated, is also provided with a clip 22 by means of whichthe rail is secured to the floor of the vehicle. Each rail 7 comprisesan elongate extrusion defining a channel having an elongate open top 23.

Each carriage 6 comprises a lower portion 24 adapted to be receivedwithin the channel defined by the rail. Appropriate ball bearings orother roller elements are located between the portion 24 of the carriage6 which is received within the channel, and the channel itself tofacilitate axial movement of the carriage along the rail.

The carriage 6 incorporates an up-standing web 25 which extendsvertically upwardly through the open top 23 of the channel. Connected tothe web 25 are the sensors 4, 5, which act to support an elongate“L”-shaped support element 26 which forms part of the sub-frame 20. Thesupport element 26 comprises a vertical flange 27, which is in alignmentwith and substantially adjacent the web 25 of the rail 6. The verticalflange 27 supports, towards the rear of the seat, a horizontallyextending pivot 28 and, towards the front of the seat, an upstandingmovable link 29 which supports, at its upper end, a horizontallyextending pivot 30. The squab 2 of the seat may be mounted on the pivots28, 30 and movement of the squab relative to the sub-frame may becontrolled by a pair of gas springs 31 (shown in phantom) connectedbetween the horizontally extending flange 32 of the support element 26and the squab of the seat. The horizontally extending flange 32 alsosupports a plate 33 which extends transversely towards the othercarriage. Two plates 33 are connected together to provide a rigidsub-frame.

It is to be appreciated, at this stage, that the sub-frame, whichcomprises the support elements 26 and the plates 33, supports the squabof the seat, and the sub-frame itself is supported on the carriages bymeans of the sensors 4 and 5. The sensors 4 and 5 thus form the soleconnection between the sub-frame and the carriages.

The sensors 4 and 5 are of the same design, and the sensor 4 isillustrated in FIG. 3. The sensor 4 comprises a lower mounting block 34provided with two oppositely outwardly apertured lugs 35 by means ofwhich the mounting block may be secured to the upstanding web 25provided on the carriage 6. The mounting block 34 presents a planarupper surface, and one end of a cantilever beam 36 rests upon that uppersurface. Above that one end of the cantilever beam 36 is a keeper plate37, and two bolts 38 are provided which extend through the keeper plate37, through the end of the cantilever beam 36 and into appropriatethreaded bores provided in the mounting block 34.

The cantilever beam 36 extends substantially parallel with the axis ofthe rail 7. The other end of the cantilever beam is sandwiched between akeeper plate 39 located beneath the end of the beam, and a horizontalface which forms the lower-most face of a mounting block 40. Themounting block 40 is provided with two oppositely and outwardly directedapertured lugs 41 by means of which the upper mounting block 40 may bemounted to the vertical flange 27 of the support element 26. A pair ofbolts 42 are provided which extend upwardly through the keeper plate 39,through the end of the cantilever beam 36 and into the mounting block40.

It will thus be understood that the entire sub-frame 20, and the seatsupported by the sub-frame 20, is supported from the carriage by meansof four cantilever beams 36. The cantilever beams 36 are provided withsensors 43 provided on the surface of the cantilever beams 36 which areresponsive to distortion or deformation of the cantilever beams 36. Thesensors may, for example, comprise resistive material, the resistance ofwhich is dependent upon the tensile forces applied to the material. Thesensors may comprise piezo electric material which provide a potentialin dependence upon the stress or pressure applied to the piezo electricmaterial. The cantilever beam 36 thus forms a load cell.

FIG. 4 illustrates a modified sensor where the mounting blocks and thecantilever element are all formed integrally.

Thus, referring to FIG. 4, an alternative sensor comprises an integralcomponent 50 comprising a first substantially rectangular mounting block51 having a substantial horizontal extent, the block 51 being providedwith horizontal bores 52, 53 at the opposed ends thereof by means ofwhich the block 51 may be secured to the upstanding web 25 provided onthe carriage 6. At one end of the mounting block 51 there is provided anupwardly directed extension 54 having a width which is substantiallyless than the length of the block 51, the extension 54 merging into asecond substantially horizontally extending cantilever block 55 whichlies over the first block 51. A substantial part of the cantilever block55 is spaced from the block 51 by means of a gap 56. A centrally locatedhorizontal bore 57 extends through the cantilever block 55. Sensorelements 58 are mounted on the side wall of the bore 57 of thecantilever block 55. The sensor elements 58 may be of the same type asdescribed with reference to FIG. 3. The end of the cantilever block 55,which is remote from the upwardly directed extension 54, is itselfprovided with a second upstanding extension 59 which serves to connectthat end of the cantilever block 55 to an upper-most horizontallyextending mounting block 60. The mounting block 60 is provided with ahorizontal bore 61 by means of which the block 60 may be bolted to thevertical flange 27 of the support element 26. There is a gap 62 betweenthe mounting block 60 and the cantilever block 55.

It will be appreciated that the central cantilever block 55 with thesensors 58 performs an equivalent function to the cantilever element 36and the sensor elements 43 of the embodiment described with reference toFIG. 3.

Turning now to FIG. 5 of the accompanying drawings, part of the carriage6 is shown in cross-section, and the lower part 24 of the carriage isshown as part of a hollow extrusion supporting the web 25. Locatedadjacent the web 25 is the upstanding flange 27 of the support element26.

A bore 70 is provided in the web 25 provided on the carriage 6. A bolt71 extends through the bore 70. The bolt 71 is provided with a threadedportion 72 of a diameter which is slightly smaller than the diameter ofthe bore 70, and this portion of the bolt passes through the bore 70.The threaded portion 72 is connected to a non-threaded portion 73 ofslightly greater diameter than the bore 70, there thus being a discreteshoulder 74 between the threaded portion 72 and the non-threadedenlarged diameter cylindrical portion 73. The shoulder 74 abuts one sideface of the web 25 adjacent the bore 70. The non-threaded cylindricalportion 73 carries an enlarged hexagonal head 75. There is a clearancegap between the head 75 and the web 25 of the carriage 6.

The threaded portion 72 carries a washer 76 which abuts against theother face of the web 25 and a nut 77 which holds the washer in place.

The cylindrical portion 73 of the bolt of enlarged diameter extendsthrough an aperture 78 formed in the vertical flange 27 of the supportelement 26. The aperture 78 is of greater diameter than that of thecylindrical portion 73.

A bolt arrangement as illustrated in FIG. 5 is provided, as can be seenin FIG. 2, adjacent each sensor 4 and 5.

When the seat is in use, with a person sitting on the seat, a downwardforce will be applied to each of the sensors 4 and 5, causing thecantilever element of each sensor to bend. The degree of bending isdependent upon the downward force applied to the sensor. The degree ofbending, and thus the downward force, applied to each sensor can readilybe determined and, by comparing the forces applied to the sensors 4provided at the front of the seat, and the sensors 5 provided at therear of the seat, it is possible to determine the position of the centreof gravity of the occupant of the seat. It is possible to determine ifthe centre of gravity is located in a position equivalent to that of aperson sitting fully back in the seat, or equivalent to that of a personleaning forwardly in the seat. Also, by determining the total sum of thedownward forces applied to the four sensors, it is possible to determinethe body weight of the occupant of the seat. The appropriatecalculations are carried out in the control arrangement 8 whichdetermines the manner in which the air-bag 10 will be inflated in theevent that the sensors 9 provide signals indicative of the fact that anaccident is likely to happen or an accident is happening.

In the event that an accident does arise, and if very substantial forcesare applied to the sub-frame 20 of the seat, if the sensors permit asubstantial movement of sub-frame relative to the carriages 6, thecylindrical portions 73 of the bolts 71 of enlarged diameter will engagethe apertures 78, thus preventing the sub-frame moving by more than arelatively small predetermined distance, relative to the carriages 6. Itis to be appreciated, however, that the spacing between the exteriorpart of the enlarged diameter cylindrical portions 73 of the bolts 71,and the apertures 78 is such that in ordinary use of the seat, and withpersons of ordinary weight sitting upon the seat, the external peripheryof the enlarged diameter cylindrical portion 73 of the bolts 71 do notcome into contact with the interior of the apertures 78, meaning thatthe sub-frame is supported solely by the sensors 4 and 5.

What is claimed is:
 1. A safety arrangement in a motor vehicle, the safety arrangement comprising a seat to be occupied by a passenger of the vehicle, a plurality of sensors located between the seat and the floor of the vehicle, each adapted to provide an indication of the downward force applied to it, control means adapted to initiate and control the inflation of an air-bag and adapted to receive signals from the sensors, and adapted to control the inflation of the air-bag in dependence upon the nature of the said signals, the sensors comprising means which, at least in ordinary use of the seat, form the sole connection between the seat and the floor of the motor vehicle, each sensor comprising a first portion connected directly or indirectly to the floor of the motor vehicle by being mounted on a carriage slideable along a rail mounted on the floor of the motor vehicle, and a second portion connected directly or indirectly to a sub-frame of the seat, said two portions being inter-connected by a deformable element having sensor means responsive to deformation thereof, wherein part of the carriage is located adjacent part of the sub-frame, one of a) said part of the carriage and b) said part of the sub-frame carrying a projection of a predetermined diameter, said projection being located within an aperture of slightly greater diameter formed in the other part, the arrangement being such that in the event that a substantial force is applied to the seat, the projection carried by the one part will engage the wall of the aperture carried by the other part.
 2. A safety arrangement according to claim 1, wherein the deformable element inter-connecting the first and second portions of each sensor comprises a cantilever beam adapted to deflect when a downward force is applied to the portion connected to the seat.
 3. A safety arrangement according to claim 2, wherein the cantilever beam has one end connected to a mounting block comprising said first portion, the mounting block having means securing the mounting block to part of the carriage, and has the other end connected to a mounting block, that other mounting block having means securing the mounting block to part of a sub-frame for the seat.
 4. A safety arrangement according to claim 2, wherein each sensor comprises an integral element, the integral element having a first portion mounted to a carriage slidably mountable in a rail connected to the floor of the vehicle and a second portion connected to the sub-frame of a seat, the two portions being inter-connected by the cantilever beam.
 5. An arrangement according to claim 1, wherein the said one part comprises a web carried by the carriage, and the other part comprises a flange carried by a support element forming part of the sub-frame, the carriage carrying a bolt having a threaded portion passing through a bore provided in the web and having a portion of enlarged diameter, defining a shoulder with the threaded portion, the portion of enlarged diameter extending through said aperture which is formed in a flange provided on a support element forming part of the sub-frame of the seat. 